A simple Paypal email confirm from gmail
From then on, any email from them will have a key icon in the upper left corner. With the fishing scams getting slicker all the time, that's nice to have.
The funny thing is that today when I was checking my spam folder, there was a verified pp email in it, key icon and all. At least it was easy to spot and it was genuine, should not have been in spam.
They sort really well, but when they do have a false positive for spam, it tends to be one of my more important emails. I check that folder nearly every day I am online.